At present, a large-scale parallel piston switching valve is the primary switching valve as one of cooling control components of a commercial air-conditioning system, and the application of the product in markets has been mature. But the market feedback and the technical analysis indicate that the parallel switching valve is not beneficial for reducing the cost and improving the energy utilization efficiency because of high cost, large pressure loss and other causes. So, the field of commercial control system starts to consider replacing the parallel switching valve with a rotation-type switching valve. For example, in Chinese Patent CN102042422B, a rotation-type switching valve technology which is used in the commercial cooling system is provided, whose specific working manner is as follows:
1. in a cooling steady state: a spool and a valve port of a valve body are in a force-fit state; via a switching passage in the spool, high-pressure gas enters a condenser, and low-pressure gas enters a compressor by an evaporator outlet to suction; 2. in a reversing process: the spool is presses downward to be separated from the valve body, then a gap generates between the valve body and the spool; the switching valve further rotates to reverse, at this point, the spool and the valve body do not contact, thereby ensuring successful completion of reversing; then the spool is reset under an action of a spring to make the spool and the valve port of the valve body in a pressed state; 3. in a heating steady state: the spool and the valve port of the valve body are in a force-fit state; via the switching passage in the spool, the high-pressure gas enters a heat exchanger.
In the technical solution, for avoiding a problem that in form of metal hard seal, the spool is stuck to not reverse because of the influences of impurity, temperature, lubrication and other factors, a manner of spool ejecting to spool rotating to spool resetting is adopted, which achieves the reversing aim of high flowing performance, and effectively solves the problem of reversing stuck.
However, for achieving the aim of intermittent transfer, the traditional art adopts a planetary gear, a mechanical telescoping mechanism, a thread linkage, and so on; so the structure is relatively complicated, and the cost is relatively high. Besides, because the moment and reversing pressing force generated by mechanism drive in a piece of large-scale cooling equipment are very large, after the product runs for a certain period of time, the gear and thread of a metal component are easy to wear, which influences the accuracy of running linkage, decreases the reliability of the product, and causes a hidden trouble to safety.
Meanwhile, a further problem in the traditional art is that the spool is an inverted-cone-shaped structure matching with the valve body. Because a sealing surface between the spool and the valve body makes, under an action of pressure difference between the high pressure and the low pressure of the valve, the spool subject to force towards a pressing direction, and in the large-scale commercial cooling system, the pressing force may be relatively large, it is difficult to separate the spool from the valve body by the set spring alone, and the reliability is low. And for this, how to provide a switching valve with high reliability and simple structure which is applied to a large-scale cooling control system is the problem to be solved by those skilled in the art.